Period for 11 Days - Why Biopsy

Hello, I am 48 and have always had regular periods. I have not experienced any Menopause symptoms yet, but my last period started on day 19 (usually day 26-29) and lasted 11 days. It was a normal period for three days then spotty. I am going on a trip next week so called my gyn basically for reassurance so I wouldn't worry next week. The nurse said I need to come in for an Endrometrial Biopsy on Friday just to make sure it isn't a pre-cancer. Now my mind is going crazy with maybe it's uterine cancer! Now I'm heading away for a wonderful trip and I'll be worrying about Uterine cancer!!! Can anyone offer me any reassurance that this is most probably a peri-menopause symptom and my gyn is just being extra careful. As a side note, I had an atypical pap last December and had it retested in June and it was fine. Never had an atypical pap before also.